When I got my iPhone SE about a year ago, I was quite surprised to see that an app was still available for Spectrumview from Oxford Scientific.
This is available in iOS but I don't think it is available for Android. Many years ago it was useful for VLF and lightbeam work when I needed an audio spectrum analyser. It was also going to be used at 137kHz until I blew up my beacon earlier this year! By changing the sample rate you can adjust the time shown on the screen.
It is the best audio spectrum analyser I found. It is a free app.
Amazon Prime sell these, but I gather there are several copies on sale and only some are "the genuine article". My wife wants to buy me something for Christmas and birthday (which is very near Christmas) and this seems a good idea. It is certainly better than socks!
If you know who sells the "real deal", please let me know.
At around £63 this looks excellent value, especially as it can also be used as a signal generator.
Thanks to Martin, G8JNJ, my attention has been brought to a small spectrum analyser that is well within amateur budgets. It also acts as a signal generator. Amazing. In Europe the TinySA may be obtained from the Danish Amateur Shop.
As part of their usual "something for the weekend" promotion they are showing a low cost spectrum analyser. It is years since I used one at work. OK, this is low cost, but covers 15MHz to 2.7GHz. Of all the test gear I ever used, a spectrum analyser was among the most useful.
In recent weeks I've seen several adverts on the ARRL website (I had a 30 day free trial) for test equipment made by a company called Rigol. In the UK they sell a well specified spectrum analyser for £895 plus VAT, which looks an incredible bargain for such an instrument. They also do a range of other pieces of test equipment such as scopes, waveform generators and power supplies. Although £895 is a bit out of my price range, I wonder if anyone reading this has any experience of this supplier's kit? If so, what is it like in terms of quality and reliability? If one was running a small RF design business one could set up a small, well equipped lab for a few thousand pounds with all new gear from this supplier. How do they do it?
On the GQRP Yahoo group recently there was some further mention of very simple spectrum analysers with some links to very impressive, yet simple circuits. I was recently offered an old HP analyser but it was very large, very old and quite expensive: I did not want something that might soon go wrong and take up a lot of space, but I still need something simple to allow basic spectrum measurements. Nothing too accurate is needed, just an indication of harmonic levels and the like.
In essence, a spectrum analyser boils down to a receiver with a swept oscillator with its output connected to a display such as an oscilloscope. In its most simple form it could be just a crystal set in which the tuned circuit is replaced by a varicap tuned circuit with the rectified output going to a display. The voltage applied to the varicap is a sawtooth waveform (for example derived from a 555 timer IC) which also drives the x axis of the scope: this makes the tuned circuit sweep a band of frequencies over a second or so with the receiver's rectified output connecting to the Y axis of a scope. The resulting scope trace is then a picture of the band being scanned.
Shortwave scan on the VK2ZAY mint tin spectrum analyser
An example of a simple spectrum analyser in a small mint tin is at Alan VK2ZAY's site http://www.vk2zay.net/article/256. Although Alan was doing this design for fun, the resulting circuit based around a VHF super-regen receiver in the IF is quite remarkable. It is a seriously useful piece of test equipment. This is the YouTube video of Alan describing the circuit:
More complex designs have wide dynamic range, more linear displays and narrow IF filters to improve the resolution. "You get what you pay for", but simplicity is still capable of providing something very useful.
